1. Field of the Invention
The present invention relates to an anti-icer circuit that is designed for a radar antenna and can further be used to neutralize the effects of a nuclear electromagnetic pulse or of parasitic electromagnetic fields coming from other radars transmitting in the vicinity.
2. Description of the Prior Art
Electronic scanning radar antennas are generally fitted out with a screen provided with a vertical polarization grid formed by a fine network of horizontal rectilinear conductive wires. This network of horizontal conductive wires is profitably used to make a heating grid constituting an anti-icer system for the screen. Within this heating grid, the horizontal rectilinear conductive wires are connected to one another by their ends in a series/parallel combination enabling them to be connected to the terminals of a supply source, and enabling a heating current to be made to flow in each of them. Seen from the supply source which gives the heating current, the horizontal rectilinear conductors, with their interconnection wiring, form one or more identical patterns that cover the surface of the screen. These patterns constitute turns in which an electromagnetic pulse may induce an electromotive force that must be dissipated to the ground and must have its supply source protected. A known way of doing this lies, firstly, in positioning dischargers between the ground and each terminal of the supply source and, secondly, in interposing pulse current blocking filters, in series, with the terminals of the supply source.
These protection systems, which are efficient, have the drawback of being bulky, heavy and costly. Indeed, for a screen area of the order of 2 m.sup.2 covered with two anti-icer half-circuits each consuming power of 750 Watts delivered under 140 volts DC, it is necessary to have dischargers and protection filters weighing about 25 kg occupying a volume of about 25 dm.sup.3 which is far from being negligible, especially if it is considered that these protection elements as well as the screen are often designed to be mounted on a rotary antenna support that can be driven by a rotational motion of the order of one rotation per second.
An aim of the present invention is to reduce the volume, weight and cost of the dischargers and protection filters of a radar antenna anti-icer system in seeking to achieve the reduction, by neutralization, of the amplitude of the electromotive forces induced at the terminals of an anti-icer system by an electromagnetic pulse.